Overview
Datastream uses the PostgreSQL WAL (Write Ahead Log) transaction log to read PostgreSQL streams. The log is stored in WAL files on the database server. Each record in the WAL log represents a single change to the actual data in one of the tables in the database.
Set configuration parameters for PostgreSQL WAL files
It is recommended that you apply the following configuration settings to your PostgreSQL database:
max_slot_wal_keep_size
: set this parameter (available only for PostgreSQL 13 and above) to limit the amount of storage used by the replication slot. This is particularly important for long-running transactions, which, in extreme cases, can lead to the WAL file size taking up the entire storage and crashing the database.statement_timeout
: set this parameter to a selected value to reduce latency caused by long-running transactions. You can also usestatement_timeout
as an alternative precaution measure for databases that don't supportmax_slot_wal_keep_size
.wal_sender_timeout
: set this parameter to0
(to disable the timeout) or to a value greater than or equal to 10 minutes.
If you plan to create more than 10 streams, or the number of logical replication slots that is used by other resources in addition to the number of planned streams exceeds 10, make sure to modify the following parameters:
max_replication_slots
: increase the value of this parameter, depending on the number of replication slots set for your database (you need 1 replication slot per stream). You can only setmax_replication_slots
at server start.max_wal_senders
: increase the value of this parameter, so that it's greater than the value of themax_replication_slots
parameter. You can only setmax_wal_senders
when you start the server.
What's next
- Learn more about PostgreSQL as a source.
- Learn more about configuring a source PostgreSQL database.